Problem: Omar is 3 times as old as Tiffany and is also 6 years older than Tiffany. How old is Omar?
Explanation: We can use the given information to write down two equations that describe the ages of Omar and Tiffany. Let Omar's current age be $o$ and Tiffany's current age be $t$ $o = 3t$ $o = t + 6$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $o$ is to solve the second equation for $t$ and substitute that value into the first equation. Solving our second equation for $t$ , we get: $t = o - 6$ . Substituting this into our first equation, we get the equation: $o = 3$ $(o - 6)$ which combines the information about $o$ from both of our original equations. Simplifying the right side of this equation, we get: $o = 3o - 18$ Solving for $o$ , we get: $2 o = 18$ $o = 9$.